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Journal of Neurological Sciences [Turkish] 33:(2)# 48; 214-226, 2016 http://www.jns.dergisi.org/text.php3?id=959

Clinical Neurophysiology

Evaluation of The Patellar Tendon Reflex With Reflex Hammer That Can Measure Impact Force, Muscle Vibration and CMAP

Serkan USLU1, Tunca NÜZKET1, Yalçın ALBAYRAK2, Hilmi UYSAL3 1Akdeniz Üniversitesi, Elektrik - Elektronik Mühendisliği Anabilim Dalı, Antalya, Turkey

2Sakarya Üniversitesi, Elektrik - Elektronik Mühendisliği Anabilim Dalı, Sakarya, Turkey3Akdeniz Üniversitesi, Nöroloji Anabilim Dalı, Antalya, Turkey

Summary

Purpose: The main aim of the study was to assess the Patella T Reflex by observing the correlation between the force applied to the tendon, subsequent muscle vibrations, and the reflex response. Therefore, a system was designed with the aim of evaluating three parameters: EMG Compound Muscle Action Potential (CMAP), The force which causes the muscle to vibrate, and Vibration (measured from the skin's surface). A reflex hammer (showing the moment when the reflex is triggered and the force that triggers the reflex) was used in this study. Materials and Methods: 10 healthy individuals with an average age of 30.2 ± 10 years were included in the study. The participants in this survey had no neurological disease. The force triggering the reflex is individually from the beginning of the Patella T Reflex to the end-point. A vibration sensor was placed on the muscle and the results were analyzed with an EMG measurement system. For the evaluation of the Patella T Reflex, the correlation between the force triggering the reflex and muscle vibration, EMG and muscle vibration, and EMG and the force triggering the reflex, were investigated. Results: There is not a linear relationship between vibration and force or between force and EMG (respectively, R² = 0.005, R² = 0.0003) but a linear relationship was observed between vibration and EMG (R² = 0.44). Having reached saturation point after a certain force, no differences were observed in the CMAP EMG. Discussion: The force initiates the reflex movement, but the reflex response is related to the vibration which the force created in the muscle. A linear correlation is observed between the amplitude of the reflex response and the vibration the reflex hammer creates on the muscle. Relatively brisk reflexes can be trigged with small forces but a greater trigging force does not bring about a relevant increase in CMAP EMG.

Key words: Patellar T Reflex, trigger force, vibration, CMAP EMG

Patella T Refleksinin Vuruş Gücü Ölçebilen Refleks Çekici, Kas Vibrasyonu ve BKAP İle Değerlendirilmesi

Özet

Amaç: Çalışmadan beklenen ana etki Patella T Refleksinin değerlendirilmesi için tendona uygulanan kuvvet, refleks yanıtı, kuvvet sonucunda kasta oluşan vibrasyon arasında nasıl bir ilişki olduğunun gözlemlenmesidir. Bileşik Kas Aksiyon Potansiyeli, kasta vibrasyona sebep olan kuvvet, vibrasyon (deri yüzeyinden ölçülmüştür) parametrelerinin değerlendirilmesi için bir sistem tasarımı yapılmıştır. Patella T refleksinin değerlendirilmesine yönelik trigger

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seviyeli refleks çekici (refleks tetiklenme anını ve refleksi tetikleyen kuvveti gösteren) çalışmada kullanılmıştır. Gereç ve Yöntem: Araştırmaya yaş ortalamaları 30.2±10 olan 10 sağlıklı birey dahil edilmiştir. Araştırmaya katılan katılımcıların herhangi bir nörolojik hastalığı yoktur. Patella T refleksinin başlangıcından bitiş anına kadar gözlenebilmesi için refleksi tetikleyen kuvvet tek başına değerlendirilmemiştir. Kas üzerine yerleştirilen vibrasyon sensörü ve EMG ölçüm sistemi ile birlikte sonuçlar analiz edilmiştir. Patella T Refleksnin değerlendirilmesi için; refleksi tetikleyen kuvvet – kasta oluşan vibrasyon, EMG – kasta oluşan vibrasyon ve EMG – refleksi tetikleyen kuvvet ilişkisi incelenmiştir. Sonuçlar: İnceleme sonucunda kuvvet ve vibrasyon, kuvvet ve EMG arasında doğrusal bir ilişki (sırasıyla R² = 0.005, R² = 0.0003) gözlemlenmezken, vibrasyon ve EMG arasında doğrusal bir ilişki (R² = 0.44) gözlemlenmiştir. Belirli bir kuvvet değerinden sonra satürasyon noktasına ulaşılmıştır, BKAP EMG' de bir değişiklik gözlemlenmemiştir. Tartışma: Bu bulgular çerçevesinde refleks hareketini başlatan etmenin kuvvet olduğu ancak, refleks yanıtının kuvvetin kasta oluşturduğu vibrasyonla ilişkili olduğu düşünülmektedir. Refleks çekicinin kasta oluşturduğu vibrasyon ile kas yanıtının amplitud değerleri arasında doğrusal bir ilişki bulunmuştur. Bununla alakalı olarak canlı reflekslerin küçük kuvvetlerle tetiklenebildiği ancak kuvvetteki artış ile ilişkili BKAP EMG amplitudunda bir artışa sebep olmamaktadır.

Anahtar Kelimeler: Patella T Refleks, Tetik Kuvveti, Vibrasyon, BKAP EMG INTRODUCTION

Deep tendon reflexes (DTR) are known as physiological stretch reflexes. They provide important information for assessing the person's neurological condition. So, in the literature this work is still up to date regarding the sense of the

obtained data and the evaluation of the DTR(13,17,18).

The Patella T Reflex, one of the deep tendon reflexes, is a reflex response which is obtained by hitting the patella tendon with a reflex hammer while the patient's leg from the kneecap downwards, as shown in Figure 1, is able to swing freely.

Figure 1: Patellar Tendon Reflex Formation and Structure

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There is a long history of studies on how the Patellar T Reflex should be triggered(4). To summarize the developments, Taylor introduced the first reflex hammer to the Philadelphia Neurological Society in 1888.(15) Krauss developed a new hammer design in 1894 by changing the place of the holding hammer and response transmission point.(6) Troemner et. al. in 1920 revealed two different double-sided designs of the hammer which were 100 g. in weight and 22 cm long.(16) In 1912, Babinski introduced a hammer which is very similar to the present version.

Analysis of the patellar reflex is one of the major neurological evaluations.(7) Various methods are available relating to the evaluation of the Patellar T Reflex. The moment when the reflex occurs can be assessed individually via different methods. Studies are available on the determination prior to reflex parameters or evaluation of the pendulum that occurred with the reflex. The amplitude of the motion that occurs during reflex has great importance with regard to evaluation and classification, especially in cases with muscle discomfort. Here, not only the M response but also kinesiology assessments are at the forefront(5).

One of the methods used in the investigation of the Patellar T Reflex is observing the accelerometer sensor with the reflex and pendulum together. In the study by Le Moyne et al., the reflex response is measured with the accelerometer and investigated latency differences and frequency domain analysis. A high degree of reliability in the evaluation of the system latency response which is designed in the study is very important(11).

Research shows that evaluations dependent on reflexes and the reflex response have important consequences. However, these evaluations are not sufficient and the effect which is causing the reflex should also be

examined. Kim et al examined reflex components in detail in the studies about investigating reflex structure. The parameters in this study show that reflex responses need more detailed investigation(8). Another important study by Kim et al. emphasizes that reflex assessment should be quantitative rather than empirical. In this study, the results were evaluated using mathematical analysis methods by developing a system to evaluate the effect which starts the reflex(9).

The impact force constitutes the reflex and with the effect of this force there are substantial differences between normal cases and spastic cases with regard to the angle/s. One of the main studies which describes this, is a system developed by Mamizuka et al. At the end of the study he showed that the force which starts the reflex does not have a linear relationship with the reflex itself. This is an important factor for better understanding the reflex. This study examined the value of the angle/s with relation to the force that triggers the reflex. Significant differences were found between normal cases and spastic cases(12).

There are many studies in the literature relating to the provision trigger with the releasing of hammer from the certain angles about the evaluation of the effect which creates reflex. The correlation between the EMG Amplitude which occurs as a reflex torque and the reflex response was examined. Although the values in relation forces show differences according to the study done by Mamizuka et al, the main results overlap(19).

One method is referred to as the Queen Hammer. In this method, the hammer is released to trigger from a certain angle and hits the tendon. Using this method, observations are made regarding at which angles the deep tendon reflex is triggered and the changes relating to these angles.

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One of the major results of this study is to ensure standardization. Determining the kinds of effects occuring in different people under the same conditions is a major part of the study(2).

Neurological examination of reflexes, which is one of the most basic parameters, is still an ongoing issue. In the study performed by our team, a detailed reflex evaluation system was established by examining the value of the vibration which causes transmission of the effect of the initiating force to the muscle and EMG responses received through the rectus femoris and the size of the force causing the reflex. The designed system was tested on patients with no neurological disorders and their response to the force was observed.

MATERIAL AND METHODS

Experimental Group

The voluntary experimental group participating in the study comprised 10 normal subjects with no history of neurological disorders. The average age of the group was 30.2 ± 10; the average height was 170 ± 15 cm and the average weight was 70 ± 20 kg.

Measurement Mechanism

The system needed to evaluate a reflex evaluation and triggering system. The Design Blocks are shown in Figure 2. The ‘measurement of the force which starts the reflex', which is considered to be the system's input parameter, presents to us the first evaluation findings. In this assessment, the aim is to express the parameter impact force as a 'Newton'. Therefore, the value which was read as analog, was obtained by the results of the digitizing. Hence, conversion was performed in accordance with the correlation of the force sensor used in this study.

The force sensor used was the Force Sensitive Resistor (FSR). The sensor was calibrated according to analog values.

Certain forces were applied to the sensor with the "Wagner Instruments FDX" self-calibration device. As a result of the values obtained from these forces, the sensitivity of the reflex hammer was adjusted to 2.5N and the calibration curve shown in Figure 3 was obtained.

The second parameter to be evaluated is vibration, because the force which starts the reflex is transmitted to the muscle spindles (spindle) with vibration. For this reason, a vibration sensor is placed with a separate probe on the upper part of the knee cap, the continuation of the rectus femoris muscle.

The vibration sensor used in the study was applied at a frequency of 256 Hz ‘'Do" sound and it was observed that the Fourier Analysis reflects this band. The results are shown in Figure 4.

The most important of the system design blocks is the CMAP EMG measurement system, which offers significant data because it reflects the muscle trigger response.

In the design of the CMAP EMG system block, the EMG signal which is taken from the body surface, is raised with operational amplifiers. The Upgrade value for designed amplifiers is 1000. The value of Common Mode Rejection Ratio (CMRR) is 110 dB, bandwidth is 10 - 500 Hz, sampling frequency is 1 kHz. It was observed that 50 Hz Power Line, which is also known as a city network, causes the most pollution on the signal. Therefore analog filter structure, which suppresses 49-51 Hz, is included in the design block.

Considering the three main block structures together, a new reflex hammer for the measurement of force which starts the reflex, a vibration sensor which indicates the transmission of power to the muscle and a system which makes EMG measurement from the rectus femoris muscle has been developed. The system's connection to the subject is shown in Figure 5.

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Figure 2: Measuring Assembly Study Block Diagram

Figure 3: Force Sensor Calibration Values

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Figure 4: Vibration Sensor Calibration Frequency Response

Figure 5: Connection of the System to the Subject

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As a result of these processes, design blocks have been completed with general outlines. The results obtained from the clinical measurements were used to make the necessary alterations to the system.

A software and graphical user interface design were prepared to analyze and display received data in the MATLAB. Three measured parameters are shown in real-time in the prepared interface. After the completion of the measurement, the impact force is calculated according to the calibration value. This force is also used as a trigger signal. In this way, the EMG response's and the vibration's place in the pattern is automatically detected. The vibration that occurs without impact force and the EMG response (due to background noise etc.) were not included in the analysis report output.

Method

In the records obtained, surface electrodes are placed in the belly of the rectus femoris muscle and a reference electrode is placed about five cm below this.

Volunteers participating in the study rested for a minimum of 15 minutes prior to measurement. The measurements were recorded while the volunteers were seated on a flat bench, 90cm above the ground. The records were made at the Akdeniz University Medical Faculty EMG Laboratory. The study was approved by Akdeniz University ethics committee and the whole team accepted the Declaration of Helsinki.

The Patellar T Reflex was triggered by different forces during the measurement.

10 different trace records were made of each occurrence. The measurement mechanism was referred to as a Reflex Evaluation System by our team. In the system;

• CMAP EMG,

• Vibration, and

• Trigger - strength values were recorded.

The biggest deciding factor for the parameters of the triple assessment system was the fact that the reflex can be evaluated in one system from the beginning through to the end. Therefore, the reflex hammer was included in the system to observe the relationship between the force and the reflex it creates and how an interaction occurs. As the reflex is transmitted to the muscle through vibrations, this measurement was also included. Meanwhile, it was decided that the muscle's CMAP EMG, which reflects the muscle's response, should be in the measurement system. Graphical representations of three channel data obtained from four different cases are shown in Figure 6. The first channel is CMAP EMG, the second channel is vibration and the third channel is a chart of the hammer's analog value.

Statistical analysis was carried out using SPSS 18.0 software. P values <0.05 were considered statistically significant. The correlation between three parameters with different pair forms (EMG -Force, Force - Vibration, Vibration - EMG) was examined. The Pearson was applied as a correlation coefficient and a two-tailed test was performed.

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RESULTS

The results of this study were evaluated according to three different criteria; i) CMAP EMG Amplitude Value – Force Value, ii) Vibration Amplitude Value – Force Value, iii) CMAP EMG Amplitude Value – Vibration EMG Value. The results obtained from each subject's mean values and standart deviations; the amplitude of CMAP EMG was found 4.12 ± 1.71 mV (range; 2.05 – 6.67 mV), the amplitude of the vibration was found 355.32 ± 110.02 mV (range; 211.43 – 550.29), the force was found 10.35 ± 3.08 N (range; 7 – 12 N). DTR Grade range of the subjects is 1 – 3 (three subjects DTR 3 Grade, three subjects DTR 1 Grade and four subjects DTR 2 Grade). The mean values of each subject were measured and the DTR Grades are listed in Table 1. Patellar T Reflex of a subject whose DTR Grade is 1 can be triggered with not only 8.75 N but also 10.75N. This situation indicates that

establishing a relation between DTR Grade and impact force is quite difficult.

At this point, the results obtained showed that from a certain force point, the changes in the CMAP EMG amplitude are not very high, but at a point that may be accepted as stable. Moreover, it was observed that the relationship between the CMAP EMG Amplitude – Vibration Amplitude was linear (R=0.663 for cumulative assessment). A linear relationship was not observed between the force vibration and force EMG (R = 0.071, R = 0.018). All results (Vibration - EMG Forced - Vibration, Force - EMG) were assessed cumulatively.

Although there is a clustering for lower amplitudes, a linear correlation between Vibration Amplitudes and CMAP EMG Amplitudes is shown in Figure 7. As shown in Figure 8, higher CMAP EMG amplitudes can be obtained at lower forces ( CMAP EMG Amplitude 7.6 mv at 25N, CMAP EMG Amplitude 12.5 mV at 17.5

Figure 6: CMAP EMG, Vibration Sensor and Force Records of the subject

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N). All CMAP EMG amplitudes (mV) – Force (N) values are showned in Figure 8. Different vibration amplitudes were obtained with same impact forces for same

subjects. ( Vibration Amplitudes for 5 N are 440 mv and 648.68 for Subject 1) All Vibration Amplitudes (mV) – Force (N) values are showned in Figure 9.

Table 1 Data Set for mean values of each subjects

EMG Amplitude

mV

Vibration Amplitude mV

Force N DTR Grade

Subject1 6,67 550,29 9,75 3

Subject2 4,73 461,39 8,75 2

Subject3 2,34 308,26 10,75 1

Subject4 2,50 460,28 11,25 1

Subject5 3,76 394,73 18 2

Subject6 5,66 353,26 12 2

Subject7 2,05 226,80 7 2

Subject8 5,89 211,43 8 3

Subject9 2,47 295,95 8,75 1

Subject10 5,15 290,88 9,25 3

Mean ± sd; median 4.12 ± 1.71 355.32 ± 110.02 10.35 ± 3.08

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Figure 7: EMG – Vibration Correlation

Figure 8: EMG – Force Correlation?

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DISCUSSION

One of the main important findings in the study is that vibration is an important parameter for understanding the reflex mechanism. The results from the measurements show CMAP EMG – Vibration as having better linear correlation than that of CMAP EMG – Impact Force.

To understand the impact force effect on the reflex mechanism, the data sets were examined by bipartite analysis (CMAP EMG – Impact Force and Vibration – Impact Force). The CMAP EMG – Impact Force correlation results are very similar to those in the study conducted by Mamizuka et al., but in our study the effect of vibration on the reflex mechanism has also been observed.

The force measurement design has been developed for clinical use. Clinicians can use the system not only for the Patellar T

Reflex, but also for other reflex evaluations. The design developed with electronical assembly is not mechanical, as was in the studies of Mamizuka et. al. and Kim et. al. The characteristics of the impact force curve are similar to those of Mamizuka et al., but we did not need as wide a force range as in their study.

The Patellar T Reflex trigger mechanism is investigated in the studies of Tham et. al. The first study, published in 2011, used a Queen Hammer to trigger the reflex and the trigger system was based on a mechanical assembly. However, our study investigated vibration and CMAP EMG.

The importance of recording EMG data is highlighted in the study of Lim et al. Another study clarifying the importance of EMG Data and systems is that of Verschueren et. al. The importance of the EMG – Vibration relationship is highlighted in this study.(14) In our study,

Figure 9: Vibration – Force Correlation?

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vibration was used to observe impact force transmission to the muscle, whereas in their study it was used for inducing. EMG amplitudes and vibration amplitudes were compared and significant results were obtained. The correlation between vibration propagation and the direction of the trigger reflex is similar to Lance's research(10).

Another mechanical trigger system was researched by Le Moyne et al. They investigated the accelerometer data without EMG or vibration. The rifles system was triggered mechanically and data was recorded. However, neither EMG nor vibration were recorded.

The present study shows that investigating muscle response, vibration and impact force as a trigger to reflex contributes to understanding and classifying the Patellar T Reflex. In addition to this, including the accelerometer or the goniometer approach to the system is more appropriate.

The results of the study reveal that the correlation between force and vibration is not linear. This shows that the vibration wave is limited in triggering the reflex mechanism. The vibration is also measured on the skin's surface, which may affect the correlation between force and vibration. As Ertekin said; Percussion propagation velocity, the amplitude and synchronization of vibration to trigger Ia fibers could be related to that situation(3).

One of the main limitations of this research could be an insufficient number of subjects. However, the data shows homogenous results.

CONCLUSION

The amplitude of the reflex response is not directly proportional to the impact force. After a certain force, no differences were observed in the CMAP EMG, it reached saturation point. The vibration triggering the reflex displays a weak linear correlation with the impact force of the reflex hammer. A linear correlation is observed between the amplitude of the

reflex response and the vibration the reflex hammer creates on the muscle. According to the results, quick reflexes can be trigged with small forces as expected, but a greater trigging force does not bring about a relevant increase in CMAP EMG.

The scope of this study covers the formation of the Patellar Tendon Reflex and its triggers. From this research, we can gather that the system can be used not only on normal subjects, but also on those with muscle disorders.

Competing Interest

The authors declare that they have no competing interests.

Acknowledgments

The study was supported by The Scientific and Tecnological Research Council of Turkey Grant (grant number: 214 S 175).

We wish to thank Miss. Özge Koç, Mrs. Barbara Kılıç who reviewed the English for the text.

Correspondence to: Hilmi Uysal E-mail: uysalh@akdeniz.edu.tr Received by: 11 August 2015 Revised by: 15 February 2016 Accepted: 08 March 2016 The Online Journal of Neurological Sciences (Turkish) 1984-2016 This e-journal is run by Ege University Faculty of Medicine, Dept. of Neurological Surgery, Bornova, Izmir-35100TR as part of the Ege Neurological Surgery World Wide Web service. Comments and feedback: E-mail: editor@jns.dergisi.org

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